In a standard brewing process a fermentation substrate, "wort", is prepared from barley malt and, in most instances, additional carbohydrate adjunct material. The spectrum of saccharide materials in the wort depends on the characteristics of the malt that is used, the mashing conditions and the type and amount of adjunct material that is used. The adjunct material may be any appropriate form of starch or sugar.
Though maltose represents the largest percentage of the fermentable sugars derived from brewers' malt under standard mashing conditions invariably there are present in the wort additional fermentable sugars that are preferentially metabolized by the yeast. These sugars are sucrose, fructose and glucose and are hereinafter referred to as "highly fermentable sugars". However, the metabolism of these highly fermentable sugars, when present in a wort in abnormally high concentrations with respect to maltose, compared to the relative amounts of such substances in a standard wort, contribute significantly to the organoleptic properties, and hence basic character, of the resultant beer.
Also contributing to said organoleptic properties are the products obtained from the wort nitrogenous material originating from the malt. Further contributors to the organoleptic properties of the beer product are the yeast which effects the desired fermentation and the hops which are introduced into the wort during boiling thereof in the kettle.
If the amount of highly fermentable sugar, and in particular, glucose, in the wort when fermentation commences is incresed significantly, say to over 10-12%, then the fermentation response of the yeast changes significantly. As noted above the yeast preferentially metabolizes the highly fermentable sugars, especially glucose, and if the amount thereof is increased as described above, the yeast will utilize essentially the glucose during its rapid growth phase and for a period thereafter. As a consequence, although the yeast may metabolize the maltose to some degree it does not adequately develop its capability to metabolize the more complex and difficultly fermentable sugars such as maltotriose and as a result, is unable to do so efficiently, if at all, in the latter part of the fermentation. Complete generation of the components which provide the beer product with its fundamental characteristics is not achieved. In addition, such systems are proven to result in "hanging" fermentations: i.e. an incomplete fermentation wherein some of the content of sugars which are fully fermentable by yeast are not actually converted during a normal fermentation period.
It should also be noted that the difficultly fermentables, such as maltotriose, and traditionally non-fermentables, such as dextrins and the alcohol content are largely responsible for the caloric content of the desired beer product.
Beers which, inter alia, have a caloric value lower than conventional beers, usually by a third or more, are enjoying increasing popularity. The light beers usually have a reduced alcohol content, about 20% generally, but this is not sufficient to give the desired reduction in caloric value. It is, therefore, necessary to reduce the amount of non-fermentable sugars which emanate from the malt and adjunct, and which generally carry through the brewing process unchanged.
U.S. Pat. No. 3,379,534 attempts to solve this latter problem by providing a process for preparing beer wherein the amylolytic enzyme amyloglucosidase is added to the mash and/or during the fermentation step of the brewing process. This is stated to impart to the resulting beer the property to remain free from haze for periods surprisingly longer than previously possible and also imparts to the resulting beer a lower calorific value than normally produced beers due to a reduction in the dextrin content. Although a minor amount of debranching enzymes may normally be present in the brewers' mashing materials, the amount thereof and the conditions extant in the wort result in their activity being insufficient to reduce to a significant extent the dextrins in the wort. Hence it is considered necessary according to the teaching of U.S. Pat. No. 3,379,534 to add amyloglucosidase to break down the dextrins in the fermentation medium and this will result, unless specific steps to the contrary are taken, in a residue of the enzyme in the bottled beer product which residue may continue to react and this can lead to flavour instability, i.e. inconsistent product. Moreover, the introduction of additives into food products is presently causing increased concern of possible health-related effects.
A further process which produces a lower carbohydrate beer is to be found in U.S. Pat. No. 2,783,147, the disclosed process employing prolonged mashing and repeated additions of diastase for increasing the proportion of fermentable carbohydrates. These additions of diastase are followed by fermentation to produce a low carbohydrate beer, the process requiring substantial additional effort on the part of the brewer in addition to the normal brewing operations.
Yet a further process for producing a low carbohydrate alcoholic beer is disclosed in U.S. Pat. No. 3,717,471, the claimed process involving subjecting barley malt to aqueous extraction under conditions favourable to the extraction of protein whilst unfavourable to the extraction of carbohydrates, hence the amount of non-fermentable sugars extracted is reduced. A highly fermentable sugar is then added to the resulting extract to produce, effectively, a reconstituted brewers' wort low in unfermentable carbohydrates. The final step involves fermenting the wort so produced. It should be noted that the reconstituted wort comprising the combined malt extract and the highly fermentable sugar (an example being glucose) is subjected to the action of brewers' yeast to form the desired product. The main claimed advantage of this process is the fact that there can be no residual added enzymes, such as the amyloglucosidase of U.S. Pat. No. 3,379,534, in the beer product and the product is claimed to be analytically and organoleptically comparable to conventional beers. However, this process is subject to the disadvantages discussed above, inherent in malt fermentation process initiated in the presence of large amounts of highly fermentable sugars as adjunct.
Also, as is well known, even minor changes in wort composition, brewing conditions, etc. radically alter the character and consistency of the beer product. Therefore, in processes such as that described in U.S. Pat. No. 3,379,534, varying the malt extract: glucose ratio in the wort obviously results in a number of products having widely variable characteristics, reduction of the malt content being known to result in a reduction in flavour stability.
Among the many publications in the brewing field that are concerned with producing light beers is U.S. Pat. No. 4,038,420 which describes a brewing process of the double fermentation type wherein a sugar adjunct is used, (not to produce a product having a reduced residual sugar content but) to increase the throughput of a given plant, i.e. reduce costs. In the claimed process, a malt wort having a nitrogen content much higher than normal and sugar solution are generally separately and completely fermented with yeast, following which the fermented wort and fermented sugar solution are blended to provide a beer product. Although the claimed invention is directed only to the case where both malt wort and sugar solution are completely and separately fermented prior to their being blended, there is reference in the text to adding unfermented sugar solution to partially fermented malt wort, the resulting mixture is then subjected to a second fermentation in which a substantial excess (ten times the amount used in the first fermentation) of additional yeast is simultaneously added, which yeast actually effects the second fermentation.
Applicant is also aware of an article entitled "Some Effects of Wort Composition on the Rate and Extent of Fermentation by Brewing Composition on the Rate and Extent of Fermentation by Brewing Yeast" by B. H. Kirsop and M. L. Brown, J. Inst. Brew. Vol. 78, 1972, which article, as with the Pollock patent, deals primarily with the rate of speed of fermentation. The article reports the results of laboratory evaluations of the effect on some fermentation characteristics of varying a malt wort composition. The experiments effected always utilized stirred conditions which are, in fact, not commonly used commercially; static fermentations invariably being used. It was found that the time required to ferment worts of various compositions to a given extent (always leaving&gt;4% residuals sugars as is usual in the United Kingdom) depends upon the extent of exponential growth in the early stages of fermentation and that growth was dependent on the concentration of assimilable nitrogen. The nitrogen concentration in the wort was varied by adding to the wort, via a one-shot procedure, quantities of carbohydrate material, (which, in effect reduced the nitrogen-containing fraction), including mainly maltose (the major fermentable carbohydrate from malt) and also glucose. It was found that the yeast produced during exponential growth in the malt wort was able to ferment rapidly much greater quantities of readily and highly fermentable carbohydrate than was present in that wort. Moreover, it was also concluded that the yeast strains evaluated ferment equally well when either maltose or glucose is added to the malt wort; and, moreover, the result was the same whether the said carbohydrate was added prior to fermentation or toward the end. The sole exception was a yeast strain which was known to attenuate poorly and which, for example, normally failed to utilize maltatriose, one of the difficultly fermentable carbohydrates from malt. In summary, the article teaches that, if sufficient assimilable nitrogen is present in the wort the yeast growth during the exponential phase is adequate to rapidly ferment the maltose from the malt and additional glucose introduced into the wort anytime during the fermentation.
An object of the present invention is to provide a brewing process capable of producing any one of a desired variety of beers having different characteristics which process is advantageously used to produce the commonly termed "light" beers.
Another object of the present invention is to provide a brewing process wherein a significant portion of the malt extract in the wort can be replaced by a highly fermentable sugar without the concomitant development of fermentation negatives.
A further object of the present invention is to provide a brewing process wherein a highly fermentable sugar is utilized as adjunct, and such adjunct can be introduced into the wort in a highly concentrated form under selected conditions whereby the yeast is spared shock which would adversely change its performance and the qualities, characteristics and consistency of the resulting alcoholic beverage.